Social media site Facebook is strengthening its foothold over the online display advertising market, as the company prepares to file for an IPO (initial public offering) in the next few days.

According to new reports, the social media giant's stake in the US display advertisement market had climbed all the way to 27.9 per cent during 2011 - almost 7 per cent up from where it stood the previous year.

This new revelation was compiled by research outfit comScore Inc., and according to its findings, the impressive growth has led to Facebook taking a huge lead over its arch rival Yahoo! whose stake in the market stood at just 11 per cent during 2011.

Google Inc. and Microsoft Corp. on the other hand fell far behind both Facebook and Yahoo!, with just 3.6 per cent and 4.5 per cent in market shares respectively.

Experts are of the opinion that the growing market shares of Facebook is due to the fact that it provides brands a free platform to connect to consumers, via Facebook pages.

"If you go back several years there was some hesitation for a lot of brands to advertise on social media. That's really changed," comScore analyst Andrew Lipsman explained, as reported by the Wall Street Journal.